Cat's eye markers generally consist of a metal casting disposed in a pocket cut into the road surface, in which is positioned a core of a resilient material such as a white or brightly colored elastomeric or rubber composition, supported entirely or partially within the rectangular or otherwise shaped cavity of the metal casting. The core generally is provided with two glass bead type reflectors which are intended to retro-reflect the headlights of approaching vehicles. The core is comprised generally of elastomeric or rubber material, such as natural rubber, and includes a portion which can wipe the front face of the glass lens as the upper marker body is depressed by the contact of a tire thereon. Lens members of the cube-corner type, if molded of glass, could be used but molded glass cube-corner reflectors do not have the accuracy or reflectivity of plastic cube-corner type reflectors and consequently for many years glass has not been used to make cube-corner type roadway or automotive reflectors. Plastics have supplanted glass for cube-corner reflectors for automotive and highway uses since the mid-40's. Plastic cube-corner type reflectors are advantageous over glass beads because they have a higher specific intensity than glass beads, they can be manufactured more economically and, most importantly they can be consistently molded to provide relatively uniform specific intensity, whereas glass beads vary widely in reflectance.
Such plastic is subject to abrasion. Its use as a lens element in the conventional rubber cat's eye core, where it is subjected to constant wiping action, results in wear of the front face, which degrades the reflectivity of the marker to a point where it would no longer be effective. While it has been ascertained that positioning a plastic reflector element at an appropriate angle will effect a balancing combination of wiping and abrasion, such angular construction cannot conveniently be used in existing cat's eye castings because the wiping action could no longer be accomplished either by a tire or by a single wiping element in the core.
It has been found advantageous to provide an abrasion-resistant surface to cover the plastic reflector to minimize abrasion.
It has also been found advantageous to provide the reflector with a radiused lower surface to minimize the abrasion that can occur when a rectangular, relatively sharp edge is repeatedly rubbed or wiped against a neoprene wiper blade. Use of such a radiused surface avoids the "digging" effect that can occur should the upward and downward movement of the core be slightly off a true vertical axis.
It has also been found advantageous to reduce stress on the core by forming tension reduction channels in the core to enable the core to flex repeatedly without tearing, and by providing a lens element which is secured to a reduced portion of the core width.
It has also been found advantageous to form the wiping element in an arcuate or curved segment to provide better contact with the reflector face.
The present invention provides an improved reflector assembly combination of a replaceable elastomeric core and a plastic cube-corner type lens element with a flat abrasion resistant surface and an elongated wiper blade integral with the base portion. An extended surface area having substantial retroreflective benefits of the cube-corner type is thus provided while at the same time preserving the retroreflectivity of the lens element during use, while enhancing durability of the core.
It therefore is an object of the present invention to provide an improved road surface marker equipped with self-wiping retroreflective cube-corner type reflectors and to provide appropriate protection for the reflectors during the automatic cleaning of the same which takes place when the core element is depressed when traveled over by vehicles such as are met in ordinary road traffic.